This invention relates to a portable punch and die jig for use in punching holes in the walls of small-diameter tubes at precisely determined locations.
Punching a hole in the wall of tubing of limited diameter at precisely the same location in a large number of such tubes so that complete uniformity can be obtained is not easy.
Such a problem arises in connection with the construction and operation of ZPR-6 and ZPR-9 which are zero-power research reactors located at Argonne National Laboratory, Argonne, Illinois.
These reactors consist of a large number of horizontally disposed tubes in which drawers containing nuclear materials are slidably disposed. The tubes are about 2 inches square having walls 0.040 inch in thickness and are welded together in groups of 25 in a square matrix. The matrix is split into two halves and the drawers contain sufficient nuclear fuel that criticality is attained when the halves of the reactor are moved together. Fuel and other nuclear materials are loaded into the proper drawers to simulate a desired reactor configuration. When Zero-Power Reactors are operated with uranium in the drawers, no cooling is required. When plutonium is placed in the drawers to simulate a plutonium-fueled configuration, cooling of the plutonium-filled drawers is required, this being accomplished by an air draft flowing through the tubes toward the rear face of the matrix. Even though the drawers are very heavy, the very remote chance that the plutonium-filled drawers might creep along the tubes due to the air draft and ultimately fall out of the tubes is one that cannot be tolerated. Thus safety considerations demand the installation of drawer stops in each tube of the existing ZPR matrix. To accomplish this, holes must be drilled or punched in the walls of these tubes near the rear face thereof at precisely determined locations.
No commercially available hand drills are known which would do the job. Also, the use of a drill of any kind would create complications due to the formation of a burr at the edge of the hole, the formation of chips and the requirement for a lubricant. Thus use of a punch and die is indicated.
Commerically available punches are not acceptable due to the small size of the tube, the requirement for accurate positioning of the hole and the need for applying considerable leverage to the punch so that punching can be accomplished manually.
It will be observed that the problem described above arose in connection with a matrix of tubes which were already welded in place. To punch each tube before incorporation in the matrix would simplify matters in some ways but would require very careful placement of the tubes in the matrix so that holes in adjacent tubes lined up so that a drawer stop could be placed therein.
While the portable punch and die jig has been described herein with respect to a specific problem which arose in the course of operation of a Zero-Power Reactor, it will be at once appreciated that the tool of the present invention is not limited to such use but could be used anywhere a similar problem arose.